U.S. patent application number 15/708922 was filed with the patent office on 2018-07-05 for surface-treated active materials and surface treatment method thereof.
The applicant listed for this patent is UNIST(ULSAN NATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY). Invention is credited to Jae Phil CHO, Seung Jun MYEONG.
Application Number | 20180190971 15/708922 |
Document ID | / |
Family ID | 62600241 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180190971 |
Kind Code |
A1 |
CHO; Jae Phil ; et
al. |
July 5, 2018 |
SURFACE-TREATED ACTIVE MATERIALS AND SURFACE TREATMENT METHOD
THEREOF
Abstract
An active material and a surface treatment method of the active
material are provided. A surface of the active material may be
treated with a coating layer including a first metal oxide
containing lithium, and a second metal oxide.
Inventors: |
CHO; Jae Phil; (Ulju-gun
Ulsan, KR) ; MYEONG; Seung Jun; (Ulju-gun Ulsan,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIST(ULSAN NATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY) |
Ulju-gun Ulsan |
|
KR |
|
|
Family ID: |
62600241 |
Appl. No.: |
15/708922 |
Filed: |
September 19, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/0402 20130101;
H01M 4/505 20130101; H01M 10/0525 20130101; H01M 4/62 20130101;
H01M 4/525 20130101; Y02E 60/10 20130101; H01M 4/0471 20130101;
H01M 4/366 20130101 |
International
Class: |
H01M 4/04 20060101
H01M004/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 30, 2016 |
KR |
10-2016-0183760 |
Claims
1. An active material having a surface treated with a coating layer
comprising a first metal oxide containing lithium, and a second
metal oxide.
2. The active material of claim 1, wherein the first metal oxide is
represented by the following Chemical Formula 1:
Li.sub.XM.sub.yO.sub.z [Chemical Formula 1] wherein M comprises at
least one selected from the group consisting of Ni, Co, Fe, Mn, Ru,
Sn, Cr, Ti, Al, P, V, S, As, Mo and W, and x, y and z are 1 to
8.
3. The active material of claim 1, wherein the second metal oxide
comprises at least one selected from the group consisting of P, S,
As, Mo, W and V.
4. The active material of claim 1, wherein the coating layer
further comprises a polyanion, the polyanion comprises at least one
of (XO.sub.4).sup.n- or (XmO.sub.3m+.sup.1).sup.n- wherein X is P,
S, As, Mo, W or V, and n and m are 1 to 4.
5. The active material of claim 1, wherein a mass ratio of the
first metal oxide:the second metal oxide ranges from 1:1 to
1:100.
6. The active material of claim 1, wherein a mass ratio of the
second metal oxide:a polyanion ranges from 1:1 to 1:100.
7. The active material of claim 1, wherein the first metal oxide
has a particle diameter of 10 nanometers (nm) to 5,000 nm.
8. A surface treatment method of an active material, the surface
treatment method comprising: preparing a precursor solution
comprising a first precursor used to generate a first metal oxide
containing lithium, and a second precursor used to generate a
second metal oxide; coating the active material with the first
precursor and the second precursor by mixing the active material
with the precursor solution; and heat-treating the active
material.
9. The surface treatment method of claim 8, wherein a mass ratio of
the first precursor:the second precursor ranges from 1:1 to
1:100.
10. The surface treatment method of claim 8, wherein the second
precursor comprises at least one selected from the group consisting
of an ammonium salt, an aniline salt, a pyridinium salt, a
methylammonium salt and an ammonium carbonate salt that are used to
generate a polyanion.
11. The surface treatment method of claim 8, wherein the first
precursor comprises at least one selected from the group consisting
of a nitride, a chloride, a sulfide, an acetate and a carbonate of
a metal.
12. The surface treatment method of claim 8, wherein the
heat-treating comprises heat-treating the active material at a
temperature of 300.degree. C. to 1000.degree. C. for 5 hours to 12
hours.
13. The surface treatment method of claim 8, wherein during the
coating, the active material comprises residual lithium on a
surface of the active material.
14. A surface treatment method of an active material, the surface
treatment method comprising: separately preparing a first precursor
solution and a second precursor solution, the first precursor
solution being used to generate a first metal oxide containing
lithium, and the second precursor solution being used to generate a
second metal oxide; coating the active material with a first
precursor by mixing the active material with the first precursor
solution and by precipitating a mixture of the active material and
the first precursor solution; coating the coated active material
with a second precursor by mixing the coated active material with
the second precursor solution and by precipitating a mixture of the
coated active material and the second precursor solution; and
heat-treating the active material coated with the second
precursor.
15. The surface treatment method of claim 14, wherein the coating
of the coated active material with the second precursor comprises
coating, with the second precursor, either one or both of a surface
of the active material and a first precursor coating layer formed
by coating the active material with the first precursor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2016-0183760, filed on Dec. 30, 2016, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND
1. Field of the Invention
[0002] At least one example embodiment relates to a surface-treated
active material and a surface treatment method of an active
material.
2. Description of the Related Art
[0003] Active materials are most widely used due to their excellent
electrochemical performances as well as lifespan characteristics.
However, since active materials have low structural stability,
applying of active materials to high capacity batteries is
limited.
[0004] To enhance a performance, various lithium transition metal
oxides, for example, LiMn.sub.2O.sub.4, olivine-type lithium iron
phosphate, lithium-oxide based active materials, and the like, are
developed. The above active materials have advantages of a low
price and a high structural stability of a three-dimensional (3D)
tunnel structure, and are applicable to lithium ion secondary
batteries due to excellent output characteristics. However, the
active materials have an issue caused by a decrease in a stability
and lifespan during repetitive charging and discharging of lithium
secondary batteries. The issue may be expected to be caused by a
decomposition of an electrolyte due to moisture inside a battery or
other influences, or by an increase in an internal resistance of
the battery and degradation of active materials. In particular, an
active material may be degraded due to residual lithium on a
surface of the active material or lithium by-products (for example,
Li.sub.2CO.sub.3, LiOH, and the like).
[0005] The above residual lithium and lithium by-products may form
a resistive film and may cause swelling by generating gas in a
battery as well as gelation by reacting with a solvent (for
example, a polyvinylidene fluoride (PVDF)) in a preparation of an
anion active material slurry. Accordingly, the residual lithium and
lithium by-products may have an influence on a decrease in lifespan
characteristics of the battery.
[0006] Recently, attempts are being made to treat residual lithium
on a surface of an active material using a surface treatment, for
example, a carbon coating technology, and to enhance output and
lifespan characteristics. However, it is difficult to form a
uniform carbon coating layer, and a process cost due to carbon
coating increases.
SUMMARY
[0007] The present disclosure is to solve the foregoing problems,
and an aspect provides an active material having an enhanced
performance through a surface treatment with a metal oxide.
[0008] Another aspect provides a surface treatment method of a
surface-treated active material.
[0009] However, the problems to be solved in the present disclosure
are not limited to the foregoing problems, and other problems not
mentioned herein would be clearly understood by one of ordinary
skill in the art from the following description.
[0010] According to an aspect, there is provided an active material
having a surface treated with a coating layer including a first
metal oxide containing lithium, and a second metal oxide.
[0011] The first metal oxide may be represented by the following
Chemical Formula 1:
Li.sub.XM.sub.yO.sub.z [Chemical Formula 1]
[0012] In Chemical Formula 1, M includes at least one of Ni, Co,
Fe, Mn, Ru, Sn, Cr, Ti, Al, P, V, S, As, Mo and W, and x, y and z
are 1 to 8.
[0013] The second metal oxide may include at least one of P, S, As,
Mo, W and V.
[0014] The coating layer may further include a polyanion. The
polyanion may include at least one of (XO.sub.4).sup.n- or
(XmO.sub.3m+1).sup.n- in which X includes at least one of P, S, As,
Mo, W and V, and n and m are 1 to 4.
[0015] A mass ratio of the first metal oxide:the second metal oxide
may range from 1:1 to 1:100.
[0016] A mass ratio of the second metal oxide:a polyanion may range
from 1:1 to 1:100.
[0017] The first metal oxide may have a particle diameter of 10
nanometers (nm) to 5,000 nm.
[0018] According to another aspect, there is provided a surface
treatment method of an active material, the surface treatment
method including preparing a precursor solution including a first
precursor used to generate a first metal oxide containing lithium,
and a second precursor used to generate a second metal oxide,
coating the active material with the first precursor and the second
precursor by mixing the active material with the precursor solution
and by precipitating a mixture of the active material and the
precursor solution, and heat-treating the active material.
[0019] A mass ratio of the first precursor:the second precursor may
range from 1:1 to 1:100.
[0020] The second precursor may include at least one of an ammonium
salt, an aniline salt, a pyridinium salt, a methylammonium salt and
an ammonium carbonate salt that are used to generate a
polyanion.
[0021] The first precursor may include at least one of a nitride, a
chloride, a sulfide, an acetate and a carbonate of a metal.
[0022] The heat-treating may include heat-treating the active
material at a temperature of 300.degree. C. to 500.degree. C. for 5
hours to 12 hours.
[0023] During the coating, the active material may include residual
lithium on a surface of the active material.
[0024] According to another aspect, there is provided a surface
treatment method of an active material, the surface treatment
method including separately preparing a first precursor solution
and a second precursor solution, the first precursor solution being
used to generate a first metal oxide containing lithium, and the
second precursor solution being used to generate a second metal
oxide, coating the active material with a first precursor by mixing
the active material with the first precursor solution and by
precipitating a mixture of the active material and the first
precursor solution, coating the coated active material with a
second precursor by mixing the coated active material with the
second precursor solution and by precipitating a mixture of the
coated active material and the second precursor solution, and
heat-treating the active material coated with the second
precursor.
[0025] The coating of the coated active material with the second
precursor may include coating, with the second precursor, either
one or both of a surface of the active material and a first
precursor coating layer formed by coating the active material with
the first precursor.
[0026] Additional aspects of example embodiments will be set forth
in part in the description which follows and, in part, will be
apparent from the description, or may be learned by practice of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] These and/or other aspects, features, and advantages of the
invention will become apparent and more readily appreciated from
the following description of example embodiments, taken in
conjunction with the accompanying drawings of which:
[0028] FIG. 1 illustrates a cross section of a surface-treated
active material according to an example embodiment;
[0029] FIG. 2 is a flowchart illustrating an example of a surface
treatment method of an active material according to an example
embodiment;
[0030] FIG. 3 illustrates a cross section of a surface-treated
active material prepared based on the surface treatment method of
FIG. 2;
[0031] FIG. 4 is a flowchart illustrating another example of a
surface treatment method of an active material according to an
example embodiment;
[0032] FIG. 5 illustrates a cross section of a surface-treated
active material prepared based on the surface treatment method of
FIG. 4;
[0033] FIGS. 6A and 6B illustrate an energy dispersive X-ray
analysis (EDXA) result and an image of a surface-treated active
material prepared in Example 1 according to an example
embodiment;
[0034] FIG. 7 illustrates an X-ray diffraction (XRD) pattern of the
surface-treated active material prepared in Example 1;
[0035] FIG. 8 illustrates initial capacities of batteries
fabricated based on Example 1 and Comparative Example 1 according
to an example embodiment; and
[0036] FIGS. 9A and 9B illustrate lifespan characteristics of the
batteries fabricated based on Example 1 and Comparative Example
1.
DETAILED DESCRIPTION
[0037] Hereinafter, example embodiments of the present disclosure
will be described in detail with reference to the accompanying
drawings. When it is determined detailed description related to a
related known function or configuration they may make the purpose
of the present disclosure unnecessarily ambiguous in describing the
present disclosure, the detailed description will be omitted here.
Also, terms used herein are defined to appropriately describe the
example embodiments and thus may be changed depending on a user,
the intent of an operator, or a custom of a field to which the
present disclosure pertains. Accordingly, the terms must be defined
based on the following overall description of this specification.
Like reference numerals present in the drawings refer to the like
elements throughout.
[0038] According to an example embodiment, an active material
(hereinafter, referred to as a "surface-treated active material")
having a surface that is treated may be provided. The surface of
the active material may be treated with a metal oxide, and thus it
is possible to enhance an initial efficiency, a lifespan
characteristic and a rate characteristic.
[0039] FIG. 1 illustrates a cross section of a surface-treated
active material according to an example embodiment. The
surface-treated active material may include an active material 10,
and a coating layer 30 formed on the active material 10.
[0040] As the active material 10, all active materials applicable
in the art, for example, a lithium-oxide based active material may
be used. The lithium-oxide based active material may include, for
example, a lithium nickel oxide, a lithium manganese oxide, a
lithium cobalt oxide, and a complex oxide (for example, a
lithium-nickel based transition metal complex oxide) thereof
obtained by substituting a transition metal oxide or a portion of
transition metals with another transition metal. The active
material 10 may include, for example, LiCoO.sub.2, LiNiO.sub.2,
LiMn.sub.2O.sub.4, LiFePO.sub.4, LiFe.sub.1-xMn.sub.xPO.sub.4,
LiNi.sub.1-x-yMn.sub.xCoyO.sub.2(0.ltoreq.x<1, 0.ltoreq.y<1),
LiNi.sub.1-x-y-zCo.sub.xM.sub.1yM.sub.2zO.sub.2 (in which M.sub.1
and M.sub.2 are independently Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta,
Ma or Mo, 0.ltoreq.x<1, 0.ltoreq.y<1, and 0.ltoreq.z<1),
LiMn.sub.2-xM.sub.xO.sub.4 (in which M=Li, Mg, Al, and
0.ltoreq.x.ltoreq.0.5), LiNi.sub.xCo.sub.yMn.sub.zO.sub.2 (in which
x+y+z=1), LiNi.sub.xCo.sub.yAl.sub.zO.sub.2 (in which x+y+z=1),
LiFe.sub.1-xMn.sub.xPO.sub.4 (in which 0.ltoreq.x.ltoreq.1.0)
LiCr.sub.xMn.sub.2-xO.sub.4 (in which 0.ltoreq.x.ltoreq.0.5),
LiFe.sub.xMn.sub.2-xO.sub.4 (in which 0.ltoreq.x.ltoreq.1.0),
LiCo.sub.xMn.sub.2-xO.sub.4 (in which 0.ltoreq.x.ltoreq.1.0),
LiNi.sub.xMn.sub.2-xO.sub.4 (in which 0.ltoreq.x.ltoreq.0.5),
LiCu.sub.xMn.sub.2-xO.sub.4 (in which 0.ltoreq.x.ltoreq.0.5),
xLi.sub.2MnO.sub.3-(1-x)LiNi.sub.aCo.sub.bMn.sub.cO.sub.2 (in which
a+b+c=1), LiNiVO.sub.4, LiCoPO.sub.4, LiNiPO.sub.4, and the
like.
[0041] For example, a residual lithium layer 20 may be formed on
the surface of the active material 10.
[0042] The coating layer 30 may be stably formed on the active
material 10 by reacting with residual lithium on the surface of the
active material 10 and/or lithium by-products.
[0043] The coating layer 30 may include a first metal oxide
containing lithium, and a second metal oxide. For example, the
first metal oxide and the second metal oxide may be mixed and
included in the coating layer 30, and/or a layer of each of the
first metal oxide and the second metal oxide may be formed and
included in the coating layer 30. The coating layer 30 may have a
thickness of 1 nanometers (nm) to 10,000 nm.
[0044] The first metal oxide containing lithium may stably form the
coating layer 30 by reacting with residual lithium on the surface
of the active material 10 and/or lithium by-products, to enhance an
initial efficiency of a battery.
[0045] The first metal oxide may be represented by the following
Chemical Formula 1:
Li.sub.XM.sub.yO.sub.z [Chemical Formula 1]
[0046] In Chemical Formula 1, M includes at least one of Ni, Co,
Fe, Mn, Ru, Sn, Cr, Ti, Al, P, V, S, As, Mo and W, and x, y and z
are rational numbers, desirably 1 to 8.
[0047] The second metal oxide may enhance lifespan characteristics
and rate characteristics, and may include, for example, at least
one metal oxide among P, S, As, Mo, W and V.
[0048] A mass ratio of the first metal oxide:the second metal oxide
may range from 1:1 to 1:100. When the mass ratio is within the
above range, a stable coating layer 30 may be formed, and an effect
of simultaneously enhancing the initial efficiency and lifespan
characteristics may be obtained.
[0049] The first metal oxide may have a particle diameter of 10 nm
to 5,000 nm. When the particle diameter is within the above range,
a formation of a non-uniform coating layer 30 due to a growth of a
metal oxide may be prevented, and a stable coating layer 30 may be
formed on the active material 10.
[0050] The coating layer 30 may further include a polyanion. The
polyanion may be a precursor of the second metal oxide. For
example, a portion of the polyanion may remain in the coating layer
30 by controlling a heat treatment condition, and the like, and the
polyanion may contribute to an improvement of rate characteristics
and a capacity retention ratio.
[0051] The polyanion may include at least one of (XO.sub.4).sup.n-
or (XmO.sub.3m+1).sup.n- in which X includes one of P, S, As, Mo, W
and V, and n and m are rational numbers, for example, 1 to 4.
[0052] A mass ratio of the second metal oxide:the polyanion may
range from 1:1 to 1:100. When the mass ratio is within the above
range, a generation of gas in a battery due to a formation of an
excessively large amount of polyanion may be prevented, and
lifespan characteristics and rate characteristics may be
enhanced.
[0053] According to an example embodiment, a surface treatment
method of an active material may be provided. In the surface
treatment method, a first metal oxide may be formed through a
reaction with residual lithium on a surface of the active material,
and a second metal oxide may be formed using a polyanion precursor.
Thus, the surface of the active material may be treated with a
uniform and stable coating layer.
[0054] FIG. 2 is a flowchart illustrating an example of a surface
treatment method of an active material according to an example
embodiment. The surface treatment method of FIG. 2 may include
operation 110 of preparing a precursor solution, operation 120 of
coating the active material with a first precursor and a second
precursor, and operation 130 of heat-treating the active material.
The surface treatment method may further include a drying
operation.
[0055] In operation 110, a precursor solution including a first
precursor and a second precursor is prepared. The first precursor
may be used to generate a first metal oxide containing lithium, and
the second precursor may be used to generate a second metal
oxide.
[0056] For example, the first precursor may include at least one of
a nitride, a chloride, a sulfide, an acetate and a carbonate of a
metal. The metal may include at least one of Ni, Co, Fe, Mn, P, V,
S, As, Mo and W.
[0057] For example, the second precursor may be a precursor to
generate a polyanion, and may include at least one of an ammonium
salt, an aniline salt, a pyridinium salt, a methylammonium salt and
an ammonium carbonate salt of (XO.sub.4).sup.n- or
(XmO.sub.3m+1).sup.n-. The second precursor may include, for
example, H.sub.3PO.sub.4, NH.sub.4H.sub.2PO.sub.2O.sub.4,
(NH.sub.4).sub.2HPO.sub.4, and the like.
[0058] For example, the first precursor may include a metal with a
greater reactivity to lithium than the second precursor.
[0059] In the precursor solution, a mass ratio of the first
precursor:the second precursor may range from 1:1 to 1:100.
[0060] The precursor solution may include, for example, water
and/or an organic solvent, such as alcohol, acetone, ethylene
glycol, and the like.
[0061] For example, the precursor solution may include a precursor
with a concentration of 1 M to 5 M.
[0062] FIG. 3 illustrates a cross section of the surface-treated
active material prepared based on the surface treatment method of
FIG. 2.
[0063] Referring to FIG. 3, in operation 120, the active material
and the precursor solution are mixed and stirred, and the active
material is coated with the first precursor and the second
precursor, to form a precursor coating layer 30a. For example, the
precursor coating layer 30a may include a first precursor, and a
polyanion as a second precursor.
[0064] The surface treatment method of FIG. 2 may further include a
drying operation. In the drying operation, a solvent may be removed
by stirring a mixture of the active material and the precursor
solution while applying heat to the mixture, or by evaporating the
mixture under a reduced pressure, after operation 120. When the
solvent is removed, heat-drying may be performed in an oven. In the
drying operation, a temperature may be appropriately selected based
on a solvent of the precursor solution, and may be, for example, a
temperature of 50.degree. C. to 200.degree. C., a temperature of
60.degree. C. to 180.degree. C., or a temperature of 80.degree. C.
to 150.degree. C.
[0065] In operation 130, the active material 10 with the precursor
coating layer 30a is heat-treated, and residual lithium on the
surface of the active material 10 is reacted with the first
precursor and/or the second precursor, to form a first metal oxide.
Also, a second metal oxide is formed based on at least a portion of
the second precursor. Accordingly, the active material 10 having
the surface treated with a coating layer 30b may be obtained.
[0066] Operation 130 may be performed in air and an inert gas
atmosphere, at a temperature of 300.degree. C. to 1,000.degree. C.,
a temperature of 350.degree. C. to 800.degree. C. or a temperature
of 400.degree. C. to 600.degree. C. for 10 minutes or longer, 30
minutes or longer, or 30 minutes to 5 hours. By controlling a
temperature and time for the heat-treating, a thickness of the
coating layer 30b and a composition of a metal oxide may be
adjusted.
[0067] FIG. 4 is a flowchart illustrating another example of a
surface treatment method of an active material according to an
example embodiment. The surface treatment method of FIG. 4 may
include operation 210 of preparing a first precursor solution and a
second precursor solution, operation 220 of coating the active
material with a first precursor, operation 230 of coating the
coated active material with a second precursor, and operation 240
of heat-treating the active material. The surface treatment method
may further include a drying operation.
[0068] In operation 210, the first precursor solution and the
second precursor solution are separately prepared. Components of
each of the first precursor solution and the second precursor
solution are the same as those described above with reference to
FIG. 2.
[0069] For example, a concentration and content of each of the
first precursor solution and the second precursor solution may be
adjusted based on a composition ratio of the precursor solution
described above with reference to FIG. 3.
[0070] A mass ratio of a first precursor of the first precursor
solution:a second precursor of the second precursor solution may
range from 1:1 to 1:100.
[0071] FIG. 5 illustrates a cross section of the surface-treated
active material prepared based on the surface treatment method of
FIG. 4. Referring to FIG. 5, in operation 220, the active material
is coated with the first precursor by mixing and precipitating the
active material 10 and the first precursor solution, to form a
first precursor coating layer 40a. The first precursor coating
layer 40a may be formed first on the active material 10, and
accordingly may more easily react with residual lithium on the
active material 10, may stably form a coating layer 50a, and may
enhance an initial efficiency.
[0072] In operation 230, the second precursor solution and the
active material 10 coated with the first precursor coating layer
40a are mixed and precipitated, to form a second precursor coating
layer 40b. For example, the second precursor coating layer 40b may
be formed by coating, with the second precursor, either one or both
of the first precursor coating layer 40a and the surface of the
active material 10, and desirably coating the first precursor
coating layer 40a.
[0073] The drying operation may be performed after operation 220,
operation 230, or both, and a process condition is the same as
those described above with reference to FIG. 3.
[0074] In operation 240, the active material 10 on which a
precursor coating layer 50a is formed is heat-treated, to form the
active material 10 having the surface that is treated with a
coating layer 50b. The precursor coating layer 50a may include the
first precursor coating layer 40a and the second precursor coating
layer 40b, and the coating layer 50b may include the first metal
oxide and the second metal oxide.
[0075] The coating layer 50b may include, for example, a
combination of a first metal oxide layer and a second metal oxide
layer, a combination of a mixed layer of the first metal oxide and
the second metal oxide and the second metal oxide layer, a
combination of the first metal oxide layer, the mixed layer of the
first metal oxide and the second metal oxide and the second metal
oxide layer, or a combination of the first metal oxide layer and
the mixed layer of the first metal oxide and the second metal
oxide. Also, the coating layer 50b may further include a polyanion
in addition to the second metal oxide.
[0076] For example, operation 240 may be performed by a process
described above with reference to FIG. 3.
[0077] The surface treatment method may further include, after
operation 240, a post treatment process (for example, a grinding
process) applicable in the art to which the present disclosure
relates, however, further description of the post treatment process
is omitted herein.
EXAMPLE 1
[0078] (1) Surface Treatment of Active Material
[0079] A first precursor and a second precursor were added to a
solvent and stirring was performed, to prepare a precursor
solution. An anode active material was put into the precursor
solution and stirring was performed for 2 hours, and dried power
was dried in an oven at 110.degree. C. for 6 hours.
[0080] The dried power was put into a furnace in an air atmosphere,
and heat-treatment was performed at 800.degree. C. for 3 hours, to
acquire a surface-treated active material, for example,
LiNi.sub.0.2Co.sub.0.2Mn.sub.0.6O.sub.2. An energy dispersive X-ray
analysis (EDXA) and an X-ray diffraction (XRD) of the
surface-treated active material were measured, and an image of the
surface-treated active material and measurement results are shown
in FIGS. 6A, 6B and 7. Based on the EDXA and XRD, it is found that
the active material is coated with a metal oxide by verifying a
crystal structure and components of each of LiPVO.sub.5 and
PVO.sub.5.
[0081] (2) Fabrication of Electrode and Battery
[0082] The surface-treated active material prepared according to
Example 1 was used to fabricate an electrode and a battery. A
cathode active material (for example, graphite), a carbon black and
a polymer binder (for example, polyvinylidene fluoride (PVDF)) were
used in a mass ratio of 8:1:1, were dissolved in
N-methylpyrrolidone (NMP), and coating with a Cu foil was
performed, to fabricate a cathode.
[0083] The surface-treated active material prepared according to
Example 1, a carbon black, and a polymer binder (for example, PVDF)
were used in a mass ratio of 5:2:3, were dissolved in NMP, and
coating with an aluminum collector was performed, to fabricate an
opposite electrode. A 1.15 M LiPF.sub.6 dissolved in a mixture of
ethyl carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl
carbonate (EMC) mixed in a volume ratio of 3:4:3 was used as a
non-aqueous electrolyte solution, and a polypropylene (PP)
separator of 20 .mu.m (celgard 2400) was used as a separator, to
fabricate a lithium secondary battery.
COMPARATIVE EXAMPLE 1
[0084] A surface treatment of an active material was performed in
the same manner as in Example 1 except that a polyanion precursor
is not applied, to fabricate an electrode and a battery.
[0085] (1) Initial Efficiency Evaluation
[0086] Anodes of the batteries fabricated according to Example 1
and Comparative Example 1 were charged with a constant current of
0.1 C up to 4.6 V, and discharged up to 2 V with a constant current
of 0.1 C until a charging current reaches 0.02 C at a constant
voltage, to measure a discharge capacity. Also, an initial charge
and discharge efficiency was calculated based on a charge capacity
and a discharge capacity for a single cycle. Results are shown in
Table 1 and FIG. 8.
TABLE-US-00001 TABLE 1 Charge Discharge i.C.E Battery (mAh
g.sup.-1) (mAh g.sup.-1) (%) Comparative 283 252 89.0 Example 1
Example 1 279 263 94.3
[0087] (2) Lifespan Evaluation
[0088] The batteries fabricated according to Example 1 and
Comparative Example 1 were charged with a constant current of 0.5
C=100 mA/g at a room temperature. When a voltage of a battery
reaches 4.6 V, the battery was charged once at a constant voltage
of 4.6 V until a charging current reaches 4 mA/g (0.02 C). The
battery charged once was discharged at a constant current of 1 C
until the voltage reaches 2 V, and a discharge capacity after a
single cycle was obtained. Charging and discharging were repeated
up to 100 cycles, to measure a discharge capacity for each of the
100 cycles and to calculate a capacity retention ratio (%).
[0089] Also, a charge output and discharge output were calculated
at the room temperature due to a voltage difference caused by
charging and discharging at 0.5 C to 4 C for 10 seconds. Results
are shown in Table 2 and FIGS. 9A and 9B.
TABLE-US-00002 TABLE 2 Discharge 100.sup.th retention 25' C Rate
Battery (mAh g.sup.-1) @ 1 C (%) (4 C/0.5 C) Comparative 203 61 57%
Example 1 Example 1 197 91 65%
[0090] Referring to Table 1 and FIG. 8, an initial lifespan
characteristic of a battery to which an anode active material
having a surface treated with a metal oxide according to an example
embodiment is applied is significantly enhanced in comparison to a
battery to which the anode active material of Comparative Example 1
to which a polyanion is not applied is applied.
[0091] Also, referring to Table 2 and FIGS. 9A and 9B, the battery
to which the anode active material having the surface treated with
the metal oxide according to an example embodiment is applied, has
a high capacity retention ratio after the 100 cycles, and a rate
characteristic of the battery is hardly changed. However, in the
battery to which the anode active material of Comparative Example 1
is applied, a capacity retention ratio rapidly decreases as a
number of cycles increases.
[0092] According to example embodiments, a surface of an active
material may be treated with a metal oxide, and a surface of the
metal oxide may be treated with a lithium metal oxide formed by a
reaction with residual lithium on the surface of the active
material and with a metal oxide formed by a polyanion. Thus, a
coating layer may be stably formed, and an initial efficiency and
lifespan characteristics may be simultaneously enhanced by the
lithium metal oxide and metal oxide.
[0093] According to example embodiments, a surface of an active
material may be treated with a metal oxide layer, and thus it is
possible to simultaneously enhance an initial efficiency, lifespan
characteristics and rate characteristics.
[0094] According to example embodiments, it is possible to apply a
surface-treated active material to various active materials, for
example, a high-voltage active material, an active material for
electric vehicle batteries, an active material for lithium
secondary batteries, and the like, and possible to enhance a
stability and output characteristic of a battery.
[0095] Although a few example embodiments of the present disclosure
have been shown and described, the present disclosure is not
limited to the described example embodiments. Instead, it would be
appreciated by those skilled in the art that changes may be made to
these example embodiments without departing from the principles and
spirit of the present disclosure, the scope of which is defined by
the claims and their equivalents.
* * * * *